From 1.14+ enchanting has had some problems where at a moderate chance, a lvl 30 enchant would offer a very low level (Armour Variants at lvl 1 and Unbreaking I most commonly) and a reduced chance of top tier enchantments from 1.13.2 (Protection IV and Depth Strider III are rarely seen in 1.14.2 in comparison). This makes trying to make good tier armour very tedious and sometimes impossible due to the amount of combining that has to be done and ending up making it too expensive.
The screenshots are examples of low-tier enchants for their value, the protection III and fire protection II screenshots are common occurrences and rarely seeing their top-tier counterparts for the value of the enchant.